Mail Archives: djgpp/1998/01/19/14:30:25
Gary Smith wrote:
>
> Help..
>
> I have just changed my CPU from a Cyrix 6x86 P166+ to an AMD K6 166MHz, and
> have noticed a drop in performance with programmes written using using DJGPP
> and Allegro. The drop in performance is in the region of 20%.
>
> I have benchmarked the AMD and the Cyrix using Wintune 97, and in all the
> tests the AMD is faster than the Cyrix. eg:
>
> Floating Point Performance (MFLOPS)
> -------------------------------------------------------
> AMD K6 P166 98
> Cyrix 6x86 P166+ 52
>
> Integer Performance (MIPS)
> -----------------------------------------
> AMD K6 P166 320
> Cyrix 6x86 P166+ 250
>
> Does anyone have any ideas as to the cause of the performance drop with the
> AMD CPU ?
Could be the system bus clock speed. What speed is it running at? For
instance, I have a AMD 486 DX4-100 ( bus speed 33 MHz) and a Cyrix 486
DX2-80 ( bus speed 40 MHz), and the DX2-80 blits consistently faster
than the DX4-100, despite its slower CPU ( the rest of the hardware is
identical). I don't know what speed the AMD and Cyrix boards are
_really_ running at ( I think the Cyrix 166+ runs at 133 MHz, with a 66
MHz bus clock; could be the AMD system bus runs at 40Mhz ). It could
simply be that Cyrix motherboards have better buses than AMD.
Then again, it could be a software problem; are you running your djgpp
progs under a different DPMI host on the AMD than on the Cyrix?
--
------------ Elliott Oti ---------------
------------- http://www.fys.ruu.nl/~oti ---------
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